Manual Surface Grinder Skills

electrosteam

Registered
Registered
Joined
Feb 14, 2013
Messages
23
I am starting to get familiar with my SG and seeking some advice on skills that used to be learned on the shop floor from more experienced c0-workers.

When I put a new job on the chuck, I need to test the surface for the high point.
This seems to take forever as I move the wheel head randomly over the job slowly dropping the head to achieve first contact.
What do the experts do ?
Is it beneficial to start with a stationary wheel, or a wheel slowly rotating (I have a VSD) ?
Is a shim stock like paper or plastic film inserted between the job and the wheel useful ?

It is annoying when the last pass on a two-sided job requires the job to be slid off the chuck, scratching the bottom side.
I know, it doesn't matter, but how can I minimize it ?
Would thin plastic film, or other material, minimize the risk of this ?

The stepover percentage that should be used is a mystery to me ?
What are the trade-offs for large versus small stepover ?, as related to cut and finish ?

If I take the job off the chuck for measurement then replaced, the next cut is always more than I expected.
I have made special effort to clean everything to no avail.
Is it me or a characteristic of the process ?
What is it about me or the process that must be improved ?
Or is it just a fact of life ?

Is there a reference book available online that deals with this type of practical skill ?

Regards from sweltering Sydney,
John
 
I'm not an expert, but I can tell you some of what I've learned over the years. First I would start the machine and get it up to speed about 10 minutes before attempting to use it. The warm up period will allow everything to normalize. Any expansion of parts will be completed before you start grinding. When you are ready to start grinding I would shut off the machine, move the table out from under the wheel and stone the chuck with an extremely fine oil stone. Then wipe it with a soft cotton cloth before placing the work piece on it. I would also run a fine file across all surfaces and edges of the work piece to knock of any burrs. Then wipe it clean before placing it on the chuck. If you have a permanent magnet chuck you might want to consider putting a piece of paper on the chuck before putting the work down. Then when it's time to remove the work there's less chance of scratching the chuck.

As I'm typing this I realize the post could go on for pages and become so boring it would be useless. There are several good sources of information available. I would suggest getting a copy of the book "Grinding Technology" by S.F. Krar and J.W. Oswald. It was published by Delmar Publishers in 1974. It covers many types of grinding including surface grinding. It also gives insight as to what types of grinding wheels are available, how they are constructed, and which ones should be used on different materials. It's a great reference book. I've used it many times to select a proper wheel and learn tricks for securing and positioning odd shaped work pieces.
 
The tool and die guy site has great info/video on it http://www.thetoolanddieguy.com
It's not free but I found it very cheap for the learning I got from his site.
Suburban tools on youtube has video on surface grinding.

I often use a sticky note. The ones from my bank have their printing at the top. the paper is .002 thick and when you touch the colored part and it starts removing the color it is easy to see. Mostly this is helpful when you want to be about .001 off the chuck cause you are facing with a wheel made to face on it's side.
Most other times I just go down slowly till I "touch off" the surface. Not to worried about the high spot as anything going on to the grinder should be within .005 of flat anyway. If not the high spot might be obvious and it is then your starting point.

If your really needing to be careful with stock removal then it would be faster to sweep for the high spot on a surface plate first so you know what you are up against.
 
+1 all around. Warm up is good (minor clarification: not all part expansion is done before you start working, as the workpiece can also expand), paper is a quick way to find when the wheel is about to make contact on a piece that is already pretty flat, your surface plate can speed up that process and let you know if you need to focus on one area or even tip the part slightly before grinding one side, and Suburban Tool (on YouTube) has an excellent set of videos on surface grinding theory and practice, including shimming with cigarette paper (typically 0.001") to correct for parts that are slightly out of square.
 
Putting a piece of white paper that is well lit behind the work, and then bending down so your eye is parallel with the chuck will let you get within a few thousandths quickly. Then follow the advice above. I typically just lower it slowly with the wheel running just over the edge of the work and traverse the table while looking and listening for first contact. Disclaimer: I am a rookie at this...
 
I use loose shims of varying thickness sliding around under an irregular work piece with the chuck not turned on to support the part if it is irregular. Just crank the wheel down until you get a spark back up a few thou and proceed across the part. You will find that the cut will get heaver or lighter adjust accordingly. Heat buildup will cause a long thin part to buck up. Take it slow. I also use small blocks similar to 1,2,3 blocks to block and support the part. With 40 years of tool making and countless hours form grinding and just squaring up parts I still use cation using the surface grinder it is one of the most dangerous machines in the shop. Just the other day I had a wheel explode because I did not give it a ring test. Also I have several machinist friends that have missing fingers. So be careful.
Jack
 
Make sure the part is good and stuck on the mag chuck! Block the part if you can. Your part/project can fly off the mag chuck in the blink of an eye and do some real damage to you, project and or machine. Please be careful, make sure your project is stuck good on the mag chuck!…Dave.
 
Some good advise above. I have watched a few videos on grinding on youtube and I also have a friend that is a tool and die maker explain quite a bit to me about the grinder.

Warming up is something you should always do, stoning the chuck is a must, dressing the wheel every time.

As for the getting close to start, the piece should already be very flat, most you would need to do it check the corners and the middle to get your touch-off.
 
Make sure the part is good and stuck on the mag chuck! Block the part if you can. Your part/project can fly off the mag chuck in the blink of an eye and do some real damage to you, project and or machine. Please be careful, make sure your project is stuck good on the mag chuck!…Dave.
I have pieces of a grinding wheel that "detonated" when I was careless once. I keep it on a shelf with other reminders of mistakes or surprise accidents. I recommend doing this with any parts that get messed up through any sort lapses in safety judgment.
 
I etch it firmly in my mind, and then destroy the evidence before anyone else sees my screw up... :-|

Not really, I am open about my past mistakes to help keep others from future mistakes. I do throw away the evidence, unless it is funny enough to make others laugh when I show them...
 
Back
Top